Nonaqueous electrolyte batteries using, for a negative electrode, a graphitized material or a carbonaceous material absorbing and releasing lithium ions have been commercialized as batteries for mobile devices having a high energy density. Recently, in order to further improve the energy density of the battery, practical applications of lithium metal oxides including Ni, such as lithium nickel cobalt aluminum oxide or lithium nickel cobalt manganese oxide, have been advanced as a positive electrode active material, to replace LiCoO2 or LiMn2O4.
On the other hand, when a battery is mounted on vehicles such as cars and trains, a material forming a positive electrode and a negative electrode is required to have excellent chemical or electrochemical stability, strength, and corrosion resistance, in terms of a storage performance in a high temperature atmosphere, a cycle performance, reliably high output over a long term, and the like. The material forming the positive electrode and the negative electrode is further required to have high performances in a cold district, a high output performance in a low temperature (−40° C.) atmosphere, and a long cycle life performance. However, development of a nonvolatile and incombustible electrolytic solution has been advanced as a nonaqueous electrolyte in terms of improvement of a safety performance, but it has not yet been put to practical application, because reduction of an output characteristic, a low temperature performance, and a cycle life performance also occur.
As explained above, in order to mount the lithium ion battery on a vehicle, or the like, issues such as a durability at a high temperature, a cycle life, a safety, and an output performance need to be overcome.
Various attempts to improve the negative electrode performances of the graphitized material or the carbonaceous material, accordingly, have been made. For example, an additive is added to an electrolytic solution to suppress reductive decomposition of the electrolytic solution for a graphite negative electrode, whereby the cycle life performance is improved. In addition, in order to improve the output performance, studies of granulation of particle shape or reduction of a particle size have taken place. It is difficult, however, to reduce the particle size (the particle diameter) (e.g., a size of 10 μm or less), because the life performance is reduced due to increased reductive decomposition of the electrolytic solution at a high temperature.
In order to improve the energy density by increasing a positive electrode capacity, practical application of the lithium metal oxide including Ni such as lithium nickel cobalt aluminum oxide or lithium nickel cobalt manganese oxide has been advanced to replace LiCoO2 or LiMn2O4. When graphitized material particles are used for the negative electrode, however, in a case where the Lithium metal oxide including Ni is used for the positive electrode, the cycle life at a high temperature and the safety (in particular the internal short-circuit) are reduced, and thus it is difficult to put it into practical application of a large size secondary battery for mounting on vehicles or a stationary large size secondary battery.